Iron acts as an essential cofactor in many cellular functions of the central nervous system, such as DNA synthesis, the mitochondrial electron transport system, and neurotransmission.1 During normal aging, iron accumulates in various brain areas, with especially high concentration in the structures of the globus pallidus, red nucleus, dentate nucleus, and substantia nigra (SN).2 It is not certain yet why iron is selectively accumulated in these areas in a nonuniform manner. Dopaminergic neurons are located in a subarea of the SN and the pars compacta. Progressive loss of these neurons is a pathological hallmark of Parkinson’s disease (PD), together with abnormally high deposition of iron in this area.3 The elevated iron level in the SN of PD has been demonstrated by autopsy,2 with 7-Tesla magnetic resonance imaging,4 and by transcranial sonography.5 The abnormal accumulation of iron may be associated with oxidative stress,6 and imbalance of mechanisms controlling iron homeostasis may have a causal influence on the pathogenesis of PD.7 The iron is changed in the brain between ferrous () and ferric () states via electron exchange process. The accumulated irons participate in the fenton reaction with hydrogen peroxide and bring about oxidative stress through the reactive oxygen species (ROS). Both neuromelanin and synthetic dopamine-melanin are bound to iron with a high degree and act as a strong iron chelator and scavenger of cytoplasmic iron.8 Dopaminergic cells in the SN and ventral tegmental areas might be vulnerable to oxidative stress and selectively involved in this manner. Then the degree of oxidative stress in the iron-laden dopaminergic cells might be various depending on the location of iron in the nucleus, mitochondria, and other cytosolic organelles. Specific neurotoxin is used for the cellular model of PD in vitro. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine is a potent neurotoxin, converted by monoamine oxidase type B to the 1-methyl-4-phenylpyridinium (MPP+) in the brain. MPP+ is moved into the cell via dopamine transporter, particularly concentrated into mitochondria and therefore induces significantly decreased mitochondrial complex-I activity. Through this process, the depletion of ATP and increasing of reactive oxygen species (ROS) linking iron induces selective cell death of dopaminergic neurons.9 To elucidate the role of iron as a potential cause of PD, understanding the distribution and quantification of cellular iron is essential. However, the extremely low concentration of iron in the cell is difficult to detect and to quantify by existing microscopy. Most previous quantification studies depended on the colorimetric ferrozine-based assay using cell lysates.10,11 With a matter of concern, cellular iron level is influenced by microscopic changes in temperature or pH and may be changed by the physiological state of the cells with various chemicals.11 Moreover, the previous methods have limitations to observe the location of iron and have difficulty analyzing the amount of iron in the intracellular organelles. An analytical technique with high-resolution imaging is needed for the visualization and quantification of cellular iron elevation as the pathology of PD progresses.